Analyzing a substance and detecting its components is critical in many areas of science, particularly biochemistry. The substance to be analyzed or "analyte" typically is initially separated into its components and then each component is analyzed to identify the component.
The primary existing separation methods include liquid chromatography (LC), capillary based liquid chromatography and capillary electrophoresis (CE). The main difference between the capillary techniques is in the ability to provide efficient separations of much smaller volume samples, typically in the nanoliter range, which is several orders of magnitude less than the volume samples capable of being separated by conventional LC.
Analyzing the sample can be accomplished in a variety of ways. One of the preferred forms of analysis or detection is with a Nuclear Magnetic Resonance or NMR spectrometer since it provides a detection scheme rich with molecular information.
U.S. Pat. No. 5,283,036 to Hofmann et al. provides an apparatus for coupled liquid chromatography and nuclear magnetic resonance spectroscopy measurements. Such an apparatus, however, only is capable of analyzing samples in the 25-200 microliter (.mu.L) volume range which is several orders of magnitude greater than the volumes obtained in micro-LC or CE.
NMR spectrometers typically are not able to analyze extremely small volume samples due primarily to their inherent low sensitivity. In order to increase the sensitivity of NMR spectrometers, smaller size RF coils typically are utilized but have yet to be developed for use with nanoliter size volume samples.
Additionally, existing RF coils typically have only been utilized with static systems where the sample to be analyzed must remain stationary for a prescribed period of time, known as the acquisition time. Such existing systems typically require an acquisition time of several minutes which significantly lengthens the process time.
It therefore would be desirable to provide a method and apparatus which combines capillary separations and NMR spectroscopy for analyzing nanoliter size samples in an in-line, substantially flowing system which provides a very short acquisition time.